Update: I'm pretty convinced now I just need to return it. If you look at the second picture it looks like the rails are off centre if you compare the distance between the rails and the leather around the front bend.
I bought a new Brooks B-17, however it the Saddle Rails seem too narrow. An online search suggests brute forcing it, however I think mine are too narrow to even do that.
Seatpost is Ritchey Road, 27.2 x 300mm.
In the attached image, my original saddle is on the left and the Brooks in the two right photos.
Should I return the Saddle, or would the local bike store be able to make good of it?